Welding torch assembly

ABSTRACT

A welding torch assembly includes a mounting plate. A welding torch is mounted to the mounting plate. The welding torch includes an adjustment track fixed to the mounting plate, an adjustment body slidable relative to the adjustment track, a torch body, an electrode holder having a longitudinal axis. An electrode includes an elongated body defining a longitudinal axis. A seating end portion includes a first truncated cone. A working end portion includes a second truncated cone. The elongated body is located between the seating portion and the working portion. A retaining nut secures the electrode in the electrode holder. The electrode retaining nut contacts the angled surface of the seating end portion. A shield gas cup is secured to the torch body that forms a welding arc to melt filler wire.

This application is a divisional of U.S. application Ser. No. 14/153,190filed Jan. 13, 2014.

BACKGROUND OF THE INVENTION

A TIG (Tungsten Inert Gas) welding torch is mounted in a seam trackerand manipulated by a robot arm to melt filler wire, fusing separateworkpieces or panels of an automotive body together at a weld seam. Thewelding torch includes a tungsten electrode that should be easilyaligned in a direction transverse to the weld seam with the filler wire.When the electrode is removed from the welding torch, it is importantthat the positioning of the new electrode is repeatable to eliminatetime consuming recalibration of the welding torch.

In prior welding torches, a long electrode is employed having a lengthof about 4.25 inch. When the electrode needs to be replaced, theelectrode is removed from the welding torch and ground to remove theused portion of the electrode. Each time the electrode is ground, about50/1,000 inch of material is removed from the electrode. The electrodeis then manually repositioned in the welding torch. When the electrodeis reinstalled, a distance between a tip of the electrode and theworkpiece needs to be maintained constant to provide consistent results.The time needed to properly manually reinstall the electrode can shutdown an assembly line, losing both time and money. Additionally, afterapproximately 8 to 10 regrinds, the electrode has a length of about 3.75inch and must be replaced. This wastes a large amount of material.

A welding torch can be used to weld sheet metal workpieces together at aweld seam. In one example, the sheet metal workpieces are a roof and abody of a vehicle. Styles of vehicles are limited by the fact that thereare constraints on how much metal can be stretched. A new vehicle stylecan be created by using several pieces of metal.

SUMMARY OF THE INVENTION

In a featured embodiment, a welding torch assembly includes a mountingplate. A welding torch is mounted to the mounting plate. The weldingtorch includes an adjustment track fixed to the mounting plate, anadjustment body slidable relative to the adjustment track, a torch body,an electrode holder having a longitudinal axis. An electrode includes anelongated body defining a longitudinal axis. A seating end portionincludes a first truncated cone. A working end portion includes a secondtruncated cone. The elongated body is located between the seatingportion and the working portion. A retaining nut secures the electrodein the electrode holder. The electrode retaining nut contacts the angledsurface of the seating end portion. A shield gas cup is secured to thetorch body that forms a welding arc to melt filler wire.

In another embodiment according to the previous embodiment, the firsttruncated cone of the seating end portion defines an included angle ofabout 45° and the electrode holder includes a truncated conical recesshaving an included angle of about 45°.

In another embodiment according to any of the previous embodiments, aseat of the retaining nut engages another angled surface of the seatingend portion of the electrode.

In another embodiment according to any of the previous embodiments,includes an arc length defined between a point of the electrode at theworking end portion and an upper surface of the filler wire, wherein thearc length is about 1.0 mm.

In another embodiment according to any of the previous embodiments, theadjustment track includes one of a groove and a protrusion and theadjustment body including the other of the groove and the protrusion,and the protrusion is receivable in the groove to allow the adjustmentbody to slide relative to the mounting plate to move the welding torch.

In another embodiment according to any of the previous embodiments,includes an adjustable fastener received in the adjustment slide thatprovides fine alignment between welding torch and the filler wire.

In another embodiment according to any of the previous embodiments, thetorch body includes a pair of opposing slots that receive one of a pairof arms of a fixed docking station when a new electrode is installed inthe welding torch.

In another embodiment according to any of the previous embodiments, aconstant length defined between the opposing conical end and the secondtruncated end. The constant length is about 0.875 inch+/−0.001 inch.

In another embodiment according to any of the previous embodiments, thefirst truncated cone defines an included angle of about 45°.

In another embodiment according to any of the previous embodiments, thesecond truncated cone is defined an included angle of about 30°.

In another embodiment according to any of the previous embodiments, theseating end surface is substantially planar and substantiallyperpendicular to the longitudinal axis.

In another embodiment according to any of the previous embodiments, theworking end surface is substantially planar and substantiallyperpendicular to the longitudinal axis.

In another embodiment according to any of the previous embodiments, theseating end portion includes a circumferential surface and an angledsurface located between the circumferential surface and the elongatedbody. The circumferential surface is located between the first truncatedcone and the angled surface, and the angled surface defines an includedangle of about 90°.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a welding torch assembly that welds togetherworkpieces;

FIG. 2 illustrates an exploded view of the welding torch;

FIG. 3 illustrates an assembled view of the welding torch, with anelectrode, an electrode retaining nut and a gas shield cup removed;

FIG. 4 illustrates the electrode;

FIG. 5 illustrates a perspective view of a torch body;

FIG. 6 illustrates an opposing perspective view of the torch body;

FIG. 7 illustrates a close up view of FIG. 7 illustrating fine movementof the electrode relative to the filer wire;

FIG. 8 illustrates an arrangement of the electrode and the filler wire;

FIG. 9 illustrates the electrode seated in an electrode holder;

FIG. 10 illustrates an electrode retaining nut fitted over theelectrode;

FIG. 11 illustrates a gas shield cup secured to the torch body;

FIGS. 12 to 26 illustrate a method of changing an electrode of thewelding torch; and

FIG. 27 illustrates a servo slide that holds sockets that are employedto change the electrode of the welding torch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, a TIG (tungsten insert gas) welding torch assembly10 is mounted on a seam tracker 12 (shown schematically in FIG. 2) andis manipulated by a robot arm (not shown) to melt a feed of filler wire16 into a welding bead to form a weld seam 99 to weld together two sheetmetal workpieces 18. In one example, the filler wire 16 is bronze oraluminum alloy, and the workpieces 18 are a zinc coated steel or analuminum alloy, respectively.

A guide arm 20 introduces the filler wire 16 under a tungsten electrode22 (shown in FIGS. 2 and 3) installed in a welding torch 24 of thewelding torch assembly 10. As explained below, the welding torch 24 canbe slid to align the electrode 22 with the filler wire 16. The electrode22 and the filler wire 16 must be precisely aligned to a preset value.

The electrode 22 is precisely machined to provide repeatable results. Avertical gap, or arc length B, is defined between a point of theelectrode 22 and a lower surface 25 of the filler wire 16, and the arclength B must be maintained for repeatable welding results. In oneexample, the arc length B is approximately 1.0 mm. Additionally, themethod of removing and replacing the electrode 22 is repeatable suchthat no additional alignment steps are required before the weldingprocess can be restarted.

FIGS. 2 and 3 illustrate the welding torch 24. The welding torch 24 ismounted to an electrically insulating mounting plate 26 that secures thewelding torch 24 to the seam tracker 12. An adjustment track 28including a dovetailed shape groove 30 is mounted to the mounting plate26 by a fastener (not shown). In one example, the fastener is a bolt.

An adjustment body 34 is attached to the adjustment track 28 andslidable relative to the adjustment track 28. The adjustment body 34includes a protrusion 36 that is received in the groove 30 of theadjustment track 28. In another example, the adjustment track 28includes the protrusion 36, and the adjustment body 34 includes thegroove 30. When the protrusion 36 is received in the groove 30, theadjustment body 34 is slidable along the adjustment track 28 to alignthe welding torch 24 with the filler wire 16.

An adjustable fastener 38 provides fine adjustment and alignment betweenthe mounting plate 26 and the adjustment track 28. In one example, theadjustable fastener 38 is a graduated micrometric adjustment screw.

The welding torch 24 includes an electrode 22 and an electrode holder40. In one example, the electrode 22 is made of tungsten. However, theelectrode 22 could be many of any tungsten alloy or can be “doped” withother elements (for example, thorium, cerium, yttrium, lanthanum). Inone example, the electrode holder 40 is a water cooled copper electrodeholder 40 as copper is highly conductive. The electrode holder 40includes a flattened portion 42 that allows the water to flow throughthe electrode holder 40. In one example, the coolant is deionized waterand anti-freeze. A plurality of seals are located around the electrodeholder 40. In one example, the seals are o-rings. An electrode retainingnut 46 secures the electrode 22 relative to the electrode holder 40. Anelectrically insulative shield gas cup 48 is secured to the weldingtorch 24. In one example, the shield gas cup 48 is made of aluminum. Aseal 44 is located inside the shield gas cup 48. In one example, theseal 44 is a o-ring. To replace the electrode 22, the retaining nut 46and the gas shield cup 48 are removed.

During use, shield gas flows through a hole in the shield gas cup 48. Inone example, the shield gas is argon. A welding arc is struck, and thefiller wire 16 is melted to form a weld bead. The welding torch 24 isthen moved during welding to create a weld seam between the workpieces18.

FIG. 4 illustrates the electrode 22. The electrode 22 includes a seatingend portion 50, a working end portion 52, an elongated body 54 locatedbetween the seating end portion 50 and the working end portion 52, and alongitudinal axis A. The seating end portion 50 defines a firsttruncated cone, and the working end portion defines a second truncatedcone.

The seating end portion 50 has a seating end flat end surface 56 thatdefines a plane substantially perpendicular to the longitudinal axis A,a circumferential surface 49 that extends around the longitudinal axisA, a seating end angled surface 68 that extends between the seating endflat end surface 56 and the circumferential surface 49, and anotherseating end angled surface 58 that extends between the circumferentialsurface 49 and the elongated body 54. The seating end flat end surface56 prevents the electrode 22 from bottoming out when installed in thewelding torch 24.

The working end portion 52 is the working end from which the TIG weldingarc is struck. The working end portion 52 includes a working end flatend surface 60 that defines a plane substantially perpendicular to thelongitudinal axis A and a working end angled surface 62 that extendsbetween the working end flat end surface 60 and the elongated body 54.

The seating end flat end surface 56 has a diameter of about 0.060 inch.The seating end flat end surface 56 and the seating end angled surface68 define an included angle C of about 45°. The circumferential surface49 has a diameter of about 0.25 inch. The another seating end angledsurface 58 and the circumferential surface 49 define an included angle Dof about 90°.

The working end flat end surface 60 has a diameter of about 0.030 inch.The working end flat end surface 60 and the working end angled surface62 define an inclined angle E of 30°.

The elongated body 54 has a diameter of about 0.18 inch. A length F fromthe working end flat end surface 60 to the intersection of the seatingend angled surface 68 and the circumferential surface 49 is about 0.875inch+/−0.001 inch. The length F has a constant length that is criticallycontrolled throughout the use and the lifetime of the electrode 22. Thelength F allows the electrode 22 to protrude sufficiently from theshield gas cup 48 to allow unobstructed access to the weld area with therequired length of the welding arc, while minimizing a distance betweenthe hot working end of the electrode 22 and the liquid cooled electrodeholder 40 to facilitate heat transfer. Other lengths are possible, butthe lengths need to be consistent to provide accuracy of the arc lengthB, which is controlled within about 0.001 inch, eliminating the need forfurther adjustments after the electrode 22 is changed. As the electrode22 is shorter than prior electrodes 22, there is more control during thewelding process.

The retaining nut 46 contacts the seating end angled surface 68 of theelectrode 22 when the electrode 22 is secured in the torch body 64. Theseating end portion 50 mates precisely, concentrically and axially in amatching conical recess (truncated to about 0.030 inch diameter flat) inthe electrode holder 40. In one example, the recess has an angle ofabout 45°, which matches the included angle C of the electrode 22.Although the angle of 45° has been described, it is to be understoodthat other angles can employed. The angle of the recess and the includedangle C of the electrode 22 must match to ensure accurate mating. If theangle is too large, the area of engagement is reduced, reducing the areaof heat transfer. If the angle is too small, the contact area betweenthe electrode 22 and the electrode holder 40 increases, increasing thepossibility that the electrode 22 will stick in the electrode holder 40when the retaining nut 46 is removed.

The another seating end angled surface 58 including the 90° includedangle D mates with a matching seating on the retaining nut 46. Theincluded angle D reduces the risk of fracturing the electrode 22 due tostress during the machining process, handling or during welding.However, it is to be understood that other angles could be used.

If it is difficult or expensive to precisely control a length of theelectrode 22, a servo actuator used within the seam tracker 12 cancarefully advance the welding torch 24 until the point of the electrode22 touches the filler wire 16. A simple electrical circuit of lowvoltage and current connected between the electrode 22 and the fillerwire 16 would become “closed” when the electrode 22 and filler wire 16contact. When the closure is sensed, the servo actuator is commanded toretract the welding torch 46 a pre-determined distance to define the arclength B, thereby resulting in a controlled arc length B being set.

FIGS. 5 and 6 illustrate the torch body 64. The torch body 64 includes athrough drilled tapped hole 66 for fitment of a fastener (not shown)that secures the electrode holder 40 relative to the torch body 64. Inone example, the fastener is a screw. In one example, the tapped hole 66is a through drilled M6 tapped hole for fitment of a fastener (nowshown) that secures the electrode holder 40 in place. The tapped hole 66intersects a bore of the electrode holder 40. When the fastener isinserted into the tapped hole, the fastener engages the flattenedportion 42 of the electrode holder 40 when tightened, securing theelectrode holder 40 both longitudinally and rotationally in the torchbody 64 during when the retaining nut 46 is installed and removed.

The torch body 64 also includes an inlet port 70 for liquid coolant, aninlet port 72 for the shield gas, and an outlet port 74 for the liquidcoolant. The torch body 64 also includes a slot 76 on opposing sides ofthe torch body 64 that can be engaged by arms 78 in a fixed dockingstation 80 to protect the seamtracker 12 from torques during the removaland installation of the shield gas cup 48, the electrode 22 and theretaining nut 46, as discussed below.

FIG. 1 illustrates the welding torch 24 during use, and FIG. 7illustrates graduated fine movement of the welding torch 24 along thelongitudinal axis A of the electrode 22 relative to the axis of thefiller wire 16 by micro-metric adjustment of the adjustable fastener 38.The alignment relationship between the electrode 22 and the filler wire16 can be adjusted by moving the welding torch 24 or the guide arm 20.

As shown in FIG. 8, the arc length B is consistently maintained afterinstallation of the electrode 22 by precisely machining the electrode 22(about +/−0.001 inch). With an arc length B of typically around about1.0 mm (0.040 inch), a 2.5% variance is accurate enough for repeatableoperation of the welding process under fully automated conditions.

FIGS. 9, 10 and 11 illustrate the assembly process for installing theelectrode 22 and the shield gas cup 48. Although the welding torch 24described is generally used with a robot arm 14 or other mechanizeddevice as described below, the electrode 22, the retaining nut 46, andthe shield gas cup 48 can be installed and removed by a manual operatorif production volumes are low and maintenance of the welding torch 24 isnot severely time constrained.

During use of the welding torch 24, the electrode 22 will wear anddeteriorate over time. The wear can be determined by the appearance ofthe welding arc, a detected voltage, an algorithm or an image obtainedby a camera.

FIGS. 12 to 26 illustrate an automatic consumable changing process forchanging the electrode 22 in the welding torch 24. As shown in FIG. 12,the welding torch 24 is removed from the seam tracker 12 and moved alongarrow 100 by the robot arm 14 to be brought into alignment with thefixed docking station 80. In FIG. 13, the welding torch 24 is positionedin the fixed docking station 80 such that one of the opposing arms 78 ofthe fixed docking station 80 is received in one of the slots 76 of thewelding torch 24.

FIG. 14 shows a cup gripping socket 86 that is moved by a firstservo-controlled nut runner (not shown) upwardly along arrow 102 towardsthe welding torch 24 for engaging and gripping the cup gripping socket86. In FIG. 15, the cup gripping socket 86 is engaged with the shieldgas cup 48, and the cup gripping socket 86 is then rotatedcounter-clockwise about arrow 104 to disengage the right hand threadedshield gas cup 48 from the torch body 64 and then withdraw to permitaccess for the electrode 22 removal process. As shown in FIG. 16, thecup gripping socket 86, which now holds the shield gas cup 48, isretracted from the torch body 64 and moved downwardly away from thewelding torch 64 along arrow 108 to another location for use later.

In FIG. 17, a second servo-controlled nut runner (not shown) moves anempty electrode gripping socket 88 towards the docked welding torch 24along arrow 109 and upwardly along arrow 110 to engage the dockedwelding torch 24. In FIG. 18, the electrode gripping socket 88 isrotated counter-clockwise about arrow 112 to disengage the electrode 22and the retaining nut 46 from the right handed threaded electrode holder40. In FIG. 19, the electrode gripping socket 88 holding the electrode22 and the retaining nut 46 is moved downwardly along the arrow 114 awayfrom the welding torch 24 and away from the welding torch 24 along arrow116. The electrode gripping socket 88 can be moved to a “dump station,”where the electrode 22 and the retaining nut 46 are released into a bin.The retaining nut 46 can be recovered and reused, and the electrode 22can be collected and recycled.

In FIG. 20, an electrode replacement socket 90 that is pre-loaded with aretaining nut 46 and an electrode 22 is moved along arrow 118 by a thirdservo-controlled nut runner (not shown) to be located under the weldingtorch 24 and then moved upwardly along arrow 120 to engage the weldingtorch 24. As shown in FIG. 21, after the pre-loaded electrodereplacement socket 90 engages the welding torch 24, the pre-loadedelectrode replacement socket 90 is rotated clockwise along arrow 122 tosecure the electrode 22 and the retaining nut 46 to the torch body 64 ofthe welding torch 24. The pre-loaded electrode replacement socket 90 isdriven by a servo drive so that a precise and preset tightening torquecan be applied. In one example, the tightening torque is about 180 toabout 200 N cm. After tightening to the pre-set torque, as shown in FIG.22, the servo driven electrode replacement socket 90 disengages from theretaining nut 46. The pre-loaded electrode replacement socket 90disengages from the welding torch 24 by moving downwardly along arrow124 and away from the welding torch 24 along arrow 126, preparing thewelding torch 24 for re-fitment of the shield gas cup 48.

In FIG. 23, the first servo-controlled nut runner returns the cupgripping socket 86 that holds the shield gas cup 48 to the fixed dockingstation 80 to reinstall the shield gas cup 48 to the torch body 64 ofthe welding torch 24. The cup gripping socket 86 is moved by the firstservo-controlled nut runner along arrow 128 and then upwardly alongarrow 130 to engage the welding torch 24. In FIG. 24, the shield gas cup48 is reengaged with the welding torch 24 and rotated by the controlledtorque servo drive about arrow 132 to thread the shield gas cup 48 ontothe welding torch 24 using the controlled torque servo drive. In oneexample, the shield gas cup 48 is tightened to a torque of about 50 Ncm. In FIG. 25, the cup gripping socket 86 is withdrawn along arrow 134after the shield gas cup 48 is refitted.

FIG. 26 shows the robot arm 14 removing the welding torch 24 from thefixed docking station 80 along arrow 136. The welding torch 24 can nowbe retuned to the seam tracker 12 and can continue welding until theelectrode 22 needs replacement again. When the electrode 22 needsreplacement, the steps shown and described in FIG. 12 to FIG. 26 arerepeated. This automated method is fast, as the shield gas cup 48, theelectrode 22, and the retaining nut 46 can be removed from the weldingtorch 24 and reinstalled in the welding torch 24 in about 5 to 10seconds.

FIG. 27 illustrates the servo slide 92 that holds the cup grippingsocket 86, the electrode gripping socket 88 and a plurality of apre-loaded electrode replacement sockets 90 that are pre-installed eachwith an electrode 22 and a retaining nut 46. The servo-controlled nutrunners lift and move the sockets 86, 88 and 90 towards and away fromthe servo slide 92 and the welding torch 24 for the removal andinstallation of the parts.

The servo slide 92 holds the sockets 86, 88 and 90. A plurality apre-loaded electrode replacement sockets 90 are located on a rotarytable 94 and are each pre-loaded with a new electrode 22 and a newretaining nut 46. The rotary table 94 rotates to align the robot arm 14with one of the pre-loaded electrode replacement sockets 90.

In one example, the servo slide 92 moves to position the requiredgripping socket 86, 88 and 90 near the welding torch 24 to remove andinstall the necessary part. The servo slide 92 is moveable in thedirection X and the direction Y, and the rotary table 94 rotates in thedirection Z. The servo slide 92 moves to align each of the cup grippingsocket 86 and the electrode gripping socket 88 with the welding torch 24to remove the shield gas cup 48 and the electrode 22/retaining nut 46,respectively. The servo slide 92 then moves into the desired position,and the rotary table 94 rotates to position a pre-loaded electrodereplacement socket 90 under the welding torch 24 to install a newelectrode 22 and a new retaining nut 46. The servo slide 92 them movessuch that the cup gripping socket 86 holding the gas shield cup 48 canbe installed on the welding torch 24. Although it is described that theservo slide 92 moves, it is also possible for the welding torch 24 tomove.

In another embodiment, if the seam tracker 12 can resist the torquesapplied during the replacement of the electrode 22, then the fixeddocking station can be omitted. In this example, the robot arm 14 isprogrammed to move the welding torch 24 to the servo-controlled nutrunners, engaging and disengaging the welding torch 24 as needed. Inthis example, the arrows 100 to 134 described above can representmovement of the welding torch 24.

The welding torch 24 can be employed to weld workpieces 18 together. Inone example, the workpieces 18 includes a roof and a body of a vehicle.As the electrode 22 is smaller than prior electrodes, there is morecontrol of the welding torch 24, and therefore the welding process ismore accurate and creates welding with a more aesthetic appearance thatcan be covered by paint, eliminating the need of plastic trim to coverthe weld seam. Additionally, as the welding is more accurate and theweld seam is more aesthetic, more vehicle designs are possible assmaller pieces of metal can be used to form the vehicle.

The foregoing description is only exemplary of the principles of theinvention. Many modifications and variations are possible in light ofthe above teachings. It is, therefore, to be understood that within thescope of the appended claims, the invention may be practiced otherwisethan using the example embodiments which have been specificallydescribed. For that reason the following claims should be studied todetermine the true scope and content of this invention.

What is claimed is:
 1. A welding torch assembly comprising: anadjustment track; a welding torch mounted to the adjustment track,wherein the welding torch includes: an adjustment body slidable relativeto the adjustment track, wherein the adjustment track includes one of agroove and a protrusion, the adjustment body includes the other of thegroove and the protrusion, and the protrusion is receivable in thegroove to allow the adjustment body to slide relative to the adjustmenttrack to move the welding torch relative to the adjustment track a torchbody, an electrode holder having a longitudinal axis, an electrodeincluding an elongated body defining a longitudinal axis, a seating endportion including a first truncated cone, a working end portionincluding a second truncated cone, wherein the elongated body is locatedbetween the seating portion and the working portion, a retaining nutthat secures the electrode in the electrode holder, wherein theelectrode retaining nut contacts the angled surface of the seating endportion, and a shield gas cup secured to the torch body that forms awelding arc to melt filler wire.
 2. The welding torch assembly asrecited in claim 1 wherein the first truncated cone of the seating endportion defines an included angle of about 45° and the electrode holderincludes a truncated conical recess having an included angle of about45°.
 3. The welding torch assembly as recited in claim 1 wherein theelectrode includes a first end and an opposing second end, the angledsurface is at the first end of the electrode and another angled surfaceis the opposing second end of the electrode, and a seat of the retainingnut engages another the angled surface of the seating end portion of theelectrode.
 4. The welding torch assembly as recited in claim 1 includingan arc length defined between a point of the electrode at the workingend portion and an upper surface of the filler wire, wherein the arclength is about 1.0 mm.
 5. The welding torch assembly as recited inclaim 1 including an adjustable fastener received in the adjustmentslide that provides fine alignment between welding torch and the fillerwire.
 6. The welding torch assembly as recited in claim 1 wherein thetorch body includes a pair of opposing slots that receive one of a pairof arms of a fixed docking station when a new electrode is installed inthe welding torch.
 7. The welding torch assembly as recited in claim 1wherein a constant length defined between the opposing conical end andthe second truncated end, wherein the constant length is about 0.875inch+/−0.001 inch.
 8. The welding torch assembly as recited in claim 7wherein the first truncated cone defines an included angle of about 45°.9. The welding torch assembly as recited in claim 7 wherein the secondtruncated cone defined an included angle of about 30′.
 10. The weldingtorch assembly as recited in claim 7 wherein the seating end surface issubstantially planar and substantially perpendicular to the longitudinalaxis.
 11. The welding torch assembly as recited in claim 7 wherein theworking end surface is substantially planar and substantiallyperpendicular to the longitudinal axis.
 12. A welding torch assemblycomprising: a mounting plate; a welding torch mounted to the mountingplate, wherein the welding torch includes: an adjustment track fixed tothe mounting plate, an adjustment body slidable relative to theadjustment track, a torch body, an electrode holder having alongitudinal axis, an electrode including an elongated body defining alongitudinal axis, a seating end portion including a first truncatedcone, a working end portion including a second truncated cone, whereinthe elongated body is located between the seating portion and theworking portion, a retaining nut that secures the electrode in theelectrode holder, wherein the electrode retaining nut contacts theangled surface of the seating end portion, and a shield gas cup securedto the torch body that forms a welding arc to melt filler wire, whereinthe seating end portion includes a circumferential surface and an angledsurface located between the circumferential surface and the elongatedbody, the circumferential surface is located between the first truncatedcone and the angled surface, and the angled surface defines an includedangle of about 90°.